Within the field of the automotive aftermarket, there are numerous parts that are considered to be “non-serviceable” items. In such cases, a new part is purchased at a substantial cost to the end user. In the field of automatic transmissions, one such common device is the solenoid module assembly that controls hydraulic flow and pressure within the transmission. A typical solenoid module includes a hydraulic manifold and one or more electromechanical solenoids. The hydraulic manifold contains numerous fluid circuit passages that hydraulically communicate with the solenoids. The electromechanical solenoids control either the flow (on/off control) through the passages or regulate pressure within the passages. Typically, the solenoids are electrically connected to a terminal housing that provides for a removable connection to a wire harness, allowing for communication to the powertrain control unit (PCU).
One such assembly is described in U.S. Pat. Nos. 4,678,006 and 4,783,049. In the described device, five electrically actuated solenoid assemblies are situated on an aluminum manifold block including multiple fluid passageways. The connections for the solenoids consist of round pins that extrude upwards through a PCB and are soldered into place. The PCB interconnects to a terminal connector providing communication through a wire harness to the PCU. This particular solenoid module has been used in the Ford E4OD and 4R100 automatic transmission since 1989. It has several failure modes and is a common replacement item. These new modules typically cost $150-200 to the end user. Several companies rebuild these modules by disassembling the unit, cleaning and reassembling the components. A new PCB of similar configuration to the original is soldered into place. A rebuilt unit costs approximately $100 to the end user.
Another such assembly is described in U.S. Pat. No. 6,056,908. The described technology is for a method of producing a solenoid module assembly with similar features to the '006 and '049 patents. However, in this invention, an overmolded circuit assembly is described in place of a PCB. In the preferred embodiment, circuit tracks are formed from strips of beryllium copper and overmolded with plastic. Furthermore, connection with the solenoids and terminal connection is preferably through the use of M shaped slots in which the solenoid terminals are pressed through. Therefore, the connection between the solenoid terminal and circuit track is made by the pressure generated from the displaced slot. This forms a one-way barbed type connection that prevents easy removal of the circuit track. This is preferable because it prevents the slot from “backing off” the solenoid terminal. However, this connection style inhibits the removal of the circuit assembly for servicing. One feature of this style of connection is that instead of round terminal pins, rectangular pins are generally used.
A variation of the '908 technology is the solenoid module produced by Bosch that is used in the Ford 5R55S, 5R55W and 5R55N automatic transmissions. This module is shown in FIGS. 1 and 2. This solenoid module has high failure rates, similar to the E4OD/4R100 solenoid module described in the '006 and '049 patents. This solenoid module costs the end user between $250-400. There has been extensive interest in rebuilding this module as the failure is generally localized to at least one of the three variable force solenoids (VFS) and/or a broken circuit trace within the module. However, the circuit assembly cannot be easily removed in one piece for reuse. The circuit assembly consists of multiple circuit tracks that are placed within two plastic housings that are snapped together, sandwiching the circuit tracks into place. During the removal process, the circuit assembly flexes, which releases the snapped connections between the 2 housings, and results in the circuit tracks to fall out of location. The defective solenoids can be replaced with new, good used or rebuilt ones. Unfortunately, new ones are not available to the general public. It has also been found that a substantial failure rate exists in used ones. Therefore, even if a good used one is installed, the long-term reliability of the solenoid is not known.
Some embodiments described herein address various aspects of this technology in novel and nonobvious ways.